暗挖换乘通道对既有车站和区间影响分析

Analysis of influence of excavated transfer tunnel on existing metro structure

北京草桥地铁站为既有10号线与新建19号线、新机场线的换乘车站,新建车站与既有车站的换乘通过长距离换乘通道方式实现,换乘通道采用暗挖法施工,且紧邻区间隧道和地铁车站,施工影响较大.提出了双导洞台阶法+施工控制+深孔注浆联合保护措施,依据规范要求提出了相应的位移控制指标,建立了包含换乘通道与既有地铁结构的三维计算模型,分析了车站、隧道的竖向和水平位移的变化规律.结果表明:换乘通道临近区间隧道和地铁车站施工,除施工控制措施外,需要辅助以深孔注浆措施;区间隧道和车站的最大位移值分别为4.04和4.50 mm,小于变形控制允许值,地铁结构位移余量足够;最大位移发生在区间隧道与地铁车站连接处和地铁车站端头位置,需在现场监测中重点关注,加密该位置测点;南侧换乘通道施工引起的竖向位移和横向水平位移占位移总量66%以上,是地铁结构安全保护的关键步骤.

Beijing Caoqiao metro station is a transfer station of line 10,the newly built line 19 and new airport line.The long-distance transfer channel is used for the transfer between the new station and the existing station.Due to the fact that the channel is close to the tunnel and the metro station,and is constructed by concealed excavation method,the construction has a great impact.Joint measures including 2-heading excavation method,construction control and deep-hole grouting are proposed.Then the control standards of metro structure displacement are established.A three-dimensional FEM model is established including transfer channel and existing subway structure.The changing law of vertical and horizontal displacement under different simulated steps is analyzed.Some conclusions have been drawn.Firstly,the risk of transfer channel construction adjacent to existing metro structure is relatively large.In addition to those control measures,it is necessary to adopt grouting measures.Secondly,the maximum displacement values of the section tunnel and the station are 4.04 and 4.50 mm respectively,which are less than the allowable value of deformation control.Therefore,the displacement surplus of the subway structure is sufficient.Thirdly,the maximum displacement is located at the connection place of tunnel and station and the end-well of metro station.Thus,the monitoring points of those two places should be regenerated.Finally,the metro structure displacement caused by south transfer channel accounts for more than 66%of the total displacement.Thus,the construction of south transfer channel is the key stage for the safety protection of the subway.